Solid ink or phase change ink printers encompass various imaging devices, including copiers and multi-function devices. These printers offer many advantages over other types of image generating devices, such as laser and aqueous inkjet imaging devices. Solid ink or phase change ink printers conventionally receive ink in a solid form as pellets or as ink sticks. A color printer typically uses four colors of ink (cyan, magenta, yellow, and black, also referred to as “CMYK”).
The solid ink pellets or ink sticks, hereafter referred to as solid ink, sticks, or ink sticks, are delivered to a melting device, which is typically coupled to an ink loader, for conversion of the solid ink to a liquid. A typical ink loader includes multiple feed channels, one for each color of ink used in the printer. Each feed channel directs the solid ink within the channel toward a melting device located at the end of the channel. Solid ink at a terminal end of a feed channel contacts the melting device and melts to form liquid ink that can be delivered to a printhead. Inkjet ejectors in the printhead are operated using firing signals to eject ink onto a surface of an image receiving member.
In some printers, each feed channel has a separate insertion opening in which ink sticks of a particular color are placed and then are transported by a mechanical conveyor, gravity, or both along the feed channel to the melting device. In other solid ink printers, solid ink sticks of all colors are loaded into a single insertion port, where a mechanical sensor identifies the ink stick by physically contacting identification indicia on the ink sticks. An ink transport system then transports the ink stick to the proper feed channel for the inserted ink stick. Some printers include optical detection systems for ink stick identification. Such printers have multiple optical sources and/or multiple optical sensors fixed in each feed channel to detect identifying features of the ink sticks. However, providing and connecting multiple optical sources and sensors can be expensive and the light and sensor variability can result in errors in identifying features. Thus, improved ink stick identification is desirable.